U.S. patent number 8,949,038 [Application Number 13/813,028] was granted by the patent office on 2015-02-03 for controlling bitumen quality in solvent-assisted bitumen extraction.
This patent grant is currently assigned to ExxonMobil Upstream Research Company. The grantee listed for this patent is Tapantosh Chakrabarty, Joseph L. Feimer, Ken N. Sury. Invention is credited to Tapantosh Chakrabarty, Joseph L. Feimer, Ken N. Sury.
United States Patent |
8,949,038 |
Chakrabarty , et
al. |
February 3, 2015 |
Controlling bitumen quality in solvent-assisted bitumen
extraction
Abstract
Described herein is a method of controlling bitumen quality in a
process stream within a solvent-assisted bitumen extraction
operation, for instance a hydrocarbon stream from a froth
separation unit (FSU). Bitumen quality is a measure of the amount
of selected contaminants in the process stream. Contaminants may
include asphaltenes (comprising metal porphyrins), sulfur, and
inorganic solids (comprising inorganic elements, e.g. Si, Al, Ti,
Fe, Na, K, Mg, and Ca). First, the amounts of selected contaminants
are measured. Next, these measured values are compared to maximum
reference values. If one or more of these contaminants is higher
than the maximum reference value, at least one variable of the
solvent-assisted bitumen extraction is adjusted to improve bitumen
quality.
Inventors: |
Chakrabarty; Tapantosh
(Calgary, CA), Sury; Ken N. (Calgary, CA),
Feimer; Joseph L. (Bright's Grove, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Chakrabarty; Tapantosh
Sury; Ken N.
Feimer; Joseph L. |
Calgary
Calgary
Bright's Grove |
N/A
N/A
N/A |
CA
CA
CA |
|
|
Assignee: |
ExxonMobil Upstream Research
Company (Houston, TX)
|
Family
ID: |
43298730 |
Appl.
No.: |
13/813,028 |
Filed: |
June 23, 2011 |
PCT
Filed: |
June 23, 2011 |
PCT No.: |
PCT/US2011/041631 |
371(c)(1),(2),(4) Date: |
January 29, 2013 |
PCT
Pub. No.: |
WO2012/039804 |
PCT
Pub. Date: |
March 29, 2012 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20130168294 A1 |
Jul 4, 2013 |
|
Foreign Application Priority Data
|
|
|
|
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Sep 22, 2010 [CA] |
|
|
2714842 |
|
Current U.S.
Class: |
702/25; 73/53.01;
436/123; 436/96; 702/23; 702/32; 436/91 |
Current CPC
Class: |
G01N
33/42 (20130101); C10G 1/008 (20130101); G01N
23/223 (20130101); C10G 1/04 (20130101); C10G
21/003 (20130101); C10G 2300/202 (20130101); G01N
2223/076 (20130101); C10G 2300/44 (20130101); Y10T
436/188 (20150115); Y10T 436/14 (20150115); G01N
21/3103 (20130101); Y10T 436/145555 (20150115); C10G
2300/206 (20130101) |
Current International
Class: |
G01N
31/00 (20060101) |
Field of
Search: |
;208/390 ;73/53.01
;436/91,96,123 ;702/22,25,32 |
References Cited
[Referenced By]
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Other References
Sparks, B. D. et al. (1992) "The Effect of Asphaltene Content on
Solvent Selection for Bitumen Extraction by the SESA Process,"
Fuel, (71); pp. 1349-1353. cited by applicant .
ASTM D4807 (2010). cited by applicant.
|
Primary Examiner: McCaig; Brian
Attorney, Agent or Firm: ExxonMobil Upstream Research-Law
Department
Claims
What is claimed is:
1. A method of controlling asphaltene content, inorganic solids
content, and sulfur content in a hydrocarbon stream during a
solvent-assisted bitumen extraction, comprising: measuring (i) an
amount of nickel or vanadium, or both, in the hydrocarbon stream as
an indication of asphaltene content, and optionally estimating an
asphaltene content based on the amount of nickel or vanadium, or
both; measuring (ii) an amount of at least one of Si, Al, Ti, Ca,
Fe, Na, K, and Mg in the hydrocarbon stream as an indication of
inorganic solids content, and optionally estimating an amount of
inorganic solids based on the amount of the at least one of Si, Al,
Ti, Ca, Fe, Na, K, and Mg; measuring (iii) an amount of sulfur in
the hydrocarbon stream; and comparing the measured or estimated
amounts of (i), (ii), and (iii) to maximum reference values, and,
where the measured or estimated amounts of (i), (ii), or (iii) are
higher than the maximum reference value, adjusting at least one
variable of the solvent-assisted bitumen extraction to control the
asphaltene content, the inorganic solids content, or the sulfur
content in the hydrocarbon stream; wherein the solvent-assisted
bitumen extraction is a paraffinic froth treatment, and wherein the
hydrocarbon stream is a hydrocarbon leg from a froth separation
unit of the solvent-assisted bitumen extraction, or is a
hydrocarbon leg from a solvent recovery unit of the
solvent-assisted bitumen extraction.
2. The method of claim 1, wherein the measuring of (i), (ii) and
(iii) is effected using X-Ray Fluorescence.
3. The method of claim 1, wherein the measuring of (i), (ii) and
(iii) is effected using inductively coupled plasma, atomic
absorption, or electron spin resonance.
4. The method of claim 1, further comprising estimating the
asphaltene content based on the amount of nickel or vanadium, or
both.
5. The method of claim 1, further comprising estimating the
inorganic solids content based on the amount of the at least one of
Si, Al, Ti, Ca, Fe, Na, K, and Mg.
6. The method of claim 1, wherein the at least one variable
comprises a solvent to bitumen froth ratio.
7. The method of claim 1, wherein the at least one variable
comprises an amount of solvent.
8. The method of claim 1, wherein the at least one variable
comprises an amount of bitumen froth.
9. The method of claim 1, wherein the at least one variable
comprises bitumen froth quality.
10. The method of claim 1, wherein the at least one variable
comprises residence time in a separation vessel.
11. The method of claim 1, wherein the at least one variable
comprises temperature in a separation vessel.
12. The method of claim 1, wherein the at least one variable
comprises pressure in a separation vessel.
13. The method of claim 1, wherein the method is operated
continuously.
14. The method of claim 1, further comprising, periodically or
before the measuring (ii), identifying minerals in the hydrocarbon
stream.
15. The method of claim 14, wherein the identifying is effected by
X-Ray Fluorescence or with a Scanning Electron Microscope and
Energy Dispersive X-Ray.
16. The method of claim 14, further comprising measuring element
concentrations in the hydrocarbon stream and converting the element
concentrations to mineral concentrations.
17. The method of claim 16, wherein the conversion is effected by
multiplying each of the element concentrations by the ratio of
molecular weight of a mineral to the atomic weight of an element of
interest.
18. The method of claim 16, further comprising adding all mineral
concentrations together to obtain the amount of inorganic
solids.
19. The method of claim 1, further comprising using a calibration
relationship between an actual amount of inorganic solids, obtained
by taking offline samples, filtering solids out, and weighing dried
filtered solids, and the measured amount of inorganic solids, to
calibrate the measured amount of inorganic solids.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is the National Stage of Internationl Application
No. PCT/US2011/041631, filed Jun. 23, 2011, which claims priority
from Canadian patent application number 2,714,842 filed on Sep. 22,
2010 entitled Controlling Bitumen Quality in Solvent-Assisted
Bitumen Extraction, the entirety of which is incorporated by
reference herein.
FIELD OF THE INVENTION
The present invention is in the field of hydrocarbon extraction
from mineable deposits, such as bitumen from oil sands. More
specifically, it relates to controlling bitumen quality in
solvent-assisted bitumen extraction.
BACKGROUND OF THE INVENTION
Oil sand extraction processes are used to liberate and separate
bitumen from oil sands so that the bitumen can be further processed
to produce synthetic crude oil. Numerous oil sand extraction
processes have been developed and commercialized, many of which
involve the use of water as a processing medium. Other processes
are non-aqueous solvent-based processes. Solvent may be used in
both aqueous and non-aqueous processes.
One water-based extraction process is the Clark hot water
extraction process (the "Clark Process"). This process typically
requires that mined oil sands be conditioned for extraction by
being crushed to a desired lump size and then combined with hot
(for instance about 95.degree. C.) water and perhaps other agents
to form a conditioned slurry of water and crushed oil sands. In the
Clark Process, an amount of sodium hydroxide (caustic) may be added
to the slurry to adjust the slurry pH upwards, which enhances the
liberation and separation of bitumen from the oil sands. Other
water-based extraction processes may use other temperatures and may
include other conditioning agents, which are added to the oil sand
slurry, or may operate without conditioning agents.
Regardless of the type of water-based extraction process employed,
the process will typically result in the production of a bitumen
froth that requires treatment with a solvent. For example, in the
Clark Process, a bitumen froth stream comprises bitumen, fine
particulate solids (also referred to as mineral or inorganic
solids) and water. Certain processes use naphtha to dilute bitumen
froth before separating the product bitumen by centrifugation.
These processes are called naphtha froth treatment (NFT) processes.
Other processes use a paraffinic solvent, and are called paraffinic
froth treatment (PFT) processes, to produce pipelineable bitumen
with low levels of solids and water. In the PFT process, a
paraffinic solvent (for example, a mixture of iso-pentane and
n-pentane) is used to dilute the froth before separating the
product, diluted bitumen, by gravity. A portion of the asphaltenes
in the bitumen is also rejected by design in the PFT process and
this rejection is used to achieve reduced solids and water levels.
In both the NFT and the PFT processes, the diluted
tailings--comprising water, solids and some hydrocarbon--are
separated from the diluted product bitumen.
Solvent is typically recovered from the diluted product bitumen
component before the bitumen is delivered to a refining facility
for further processing.
One PFT process will now be described further, although variations
of the process exist. The PFT process may comprise at least three
units: Froth Separation Unit (FSU), Solvent Recovery Unit (SRU) and
Tailings Solvent Recovery Unit (TSRU). Two FSUs may be used, as
shown in FIG. 1.
With reference to FIG. 1, mixing of solvent with the feed bitumen
froth (100) is carried out counter-currently in two stages: FSU-1
and FSU-2, labeled as Froth Separation Unit 1 (102) and Froth
Separation Unit 2 (104). The bitumen froth comprises bitumen,
water, and fine solids (also referred to as mineral solids). A
typical composition of bitumen froth is about 60 wt % bitumen, 30
wt % water, and 10 wt % solids. The paraffinic solvent is used to
dilute the froth before separating the product bitumen by gravity.
Examples of paraffinic solvents are pentane or hexane, either used
alone or mixed with isomers of pentanes or hexanes, respectively.
An example of a paraffinic solvent is a mixture of iso-pentane and
n-pentane. In FSU-1 (102), the froth (100) is mixed with the
solvent-rich oil stream (101) from the second stage (FSU-2) (104).
The temperature of FSU-1 (102) is maintained at, for instance,
about 60.degree. C. to about 80.degree. C., or about 70.degree. C.,
while the solvent to bitumen (SB) ratio may be from 1.4:1 to 2.2:1
by weight or may be controlled around 1.6:1 by weight for a 60:40
mixture of n-pentane: iso-pentane. The overhead from FSU-1 (102) is
the diluted bitumen product (105) (also referred to as the
hydrocarbon leg) and the bottom stream from FSU-1 (102) is the
tailings (107) comprising water, solids (inorganics), asphaltenes,
and some residual bitumen. The residual bitumen from this bottom
stream is further extracted in FSU-2 (104) by contacting it with
fresh solvent (109), for instance, in a 25 to 30:1 (w/w) SB ratio
at, for instance, about 80.degree. C. to about 100.degree. C., or
about 90.degree. C. Examples of operating pressures of FSU-1 and
FSU-2 are about 550 kPag and 600 kPag, respectively. The
solvent-rich oil (overhead) (101) from FSU-2 (104) is mixed with
the fresh froth feed (100) as mentioned above. The bottom stream
from FSU-2 (104) is the tailings (111) comprising solids, water,
asphaltenes and residual solvent, which is to be recovered in the
Tailings Solvent Recovery Unit (TSRU) (106) prior to the disposal
of the tailings (113) in tailings ponds. The recovered solvent
(118) from TSRU (106) is directed to the solvent storage (110).
Solvent from the diluted bitumen overhead stream (105) is recovered
in the Solvent Recovery Unit (SRU) (108) and passed as solvent
(117) to Solvent Storage (110). Bitumen (115) exiting the SRU (108)
is also illustrated. The foregoing in only an example of a PFT
process and the values are provided by way of example only. An
example of a PFT process is described in Canadian Patent No.
2,587,166 to Sury.
To meet bitumen product quality, it is important for the diluted
bitumen from FSU-1 to be below a set maximum amount of
contaminants. Bitumen quality refers to the amount of selected
contaminants in the process stream. Contaminants may include
asphaltenes (comprising metal porphyrins) and inorganic solids
(comprising inorganic elements, e.g. Si, Al, Ti, Fe, Na, K, Mg, and
Ca). Achieving target bitumen quality is important as the
contaminants may adversely affect the refinery processing of the
product bitumen.
One known method of determining the solids content is to analyze
samples in a laboratory using ASTM D4807. This method is not
suitable for controlling bitumen quality while the froth is being
processed.
Canadian Patent Application No. 2,644,821 (Chakrabarty et al.)
filed on Nov. 26, 2008, published on May 26, 2010, in the name of
Imperial Oil Resources Limited, describes the use of a native
bitumen marker for controlling the SB ratio of a process stream
during solvent-assisted bitumen extraction. That application
describes using one or more native bitumen markers (for example,
sulfur, nickel, vanadium, iron, copper, manganese, or chromium) to
measure the SB in a process stream, for instance a stream from a
froth separation unit (FSU) and/or to measure hydrocarbon loss, for
instance in a tailings solvent recovery unit (TSRU).
SUMMARY OF THE INVENTION
Described herein is a method of controlling bitumen quality in a
hydrocarbon stream, for instance a hydrocarbon stream from a froth
separation unit (FSU), within a solvent-assisted bitumen extraction
operation. Bitumen quality refers to the amount of selected
contaminants in the hydrocarbon stream. Contaminants may include
asphaltenes (comprising metal porphyrins) and inorganic or mineral
solids (comprising inorganic elements, e.g. Si, Al, Ti, Fe, Na, K,
Mg, and Ca). In controlling the bitumen quality, the amount of each
selected contaminant is first measured. Next, the measured value is
compared to the maximum reference value for each contaminant. Where
one or more of these contaminants is higher than the maximum
reference value, at least one variable of the solvent-assisted
bitumen extraction is adjusted to improve bitumen quality.
In a first aspect, the present invention provides a method of
controlling asphaltene content or inorganic solids content in a
hydrocarbon stream during a solvent-assisted bitumen extraction,
comprising:
measuring (i) an amount of nickel or vanadium, or both, in the
hydrocarbon stream as an indication of asphaltene content, and
optionally estimating an asphaltene content based on the amount of
nickel or vanadium, or both;
measuring (ii) an amount of inorganic elements in the hydrocarbon
stream as an indication of inorganic solids content, and optionally
estimating an amount of inorganic solids based on the amount of
inorganic elements; and
comparing the measured or estimated amounts of (i) and (ii) to
maximum reference values, and, where the measured or estimated
amounts of (i) or (ii) are higher than the maximum reference value,
adjusting at least one variable of the solvent-assisted bitumen
extraction to control the asphaltene content or the inorganic
solids content in the hydrocarbon stream.
In certain embodiments, the following features may be present. The
measuring of (i) and (ii) may be effected using X-Ray Fluorescence,
inductively coupled plasma, atomic absorption, or electron spin
resonance. The method may comprise estimating the asphaltene
content based on the amount of nickel or vanadium, or both. The
method may comprise estimating the inorganic solids content based
on the amount of inorganic elements. The method may further
comprise measuring (iii) an amount of sulfur in the hydrocarbon
stream, and comparing the measured amount of (iii) to a maximum
reference value, and adjusting at least one variable of the
solvent-assisted bitumen extraction, if necessary, based on the
measured amount as compared to the maximum reference value. The
measuring of (iii) may be effected using X-Ray Fluorescence,
inductively coupled plasma, atomic absorption, or electron spin
resonance. The inorganic elements may comprise at least one of Si,
Al, Ti, Ca, Fe, and Mg. The inorganic elements may comprise Si, Al,
Ti, Ca, Fe, and Mg. The inorganic elements may further comprise Na
or K. The solvent-assisted bitumen extraction may be an aqueous
solvent extraction process. The hydrocarbon stream may be a
hydrocarbon leg from a froth separation unit of the
solvent-assisted bitumen extraction. The hydrocarbon stream may be
a hydrocarbon leg from a solvent recovery unit of the
solvent-assisted bitumen extraction. The solvent-assisted bitumen
extraction may be a paraffinic froth treatment. The at least one
variable may comprise a solvent to bitumen froth ratio. The at
least one variable may comprise an amount of solvent. The at least
one variable may comprises an amount of bitumen froth. The at least
one variable may comprise bitumen froth quality. The at least one
variable may comprise residence time in a separation vessel. The at
least one variable may comprise temperature in a separation vessel.
The at least one variable may comprise pressure in a separation
vessel. The solvent-assisted bitumen extraction may be a
non-aqueous solvent extraction process. The method may be operated
continuously. The method may further comprise, periodically or
before the measuring (ii), identifying minerals in the hydrocarbon
stream. The indentifying may be effected by X-Ray Fluorescence or
with a Scanning Electron Microscope and Energy Dispersive X-Ray.
The method may further comprise;
measuring element concentrations in the hydrocarbon stream and
converting the element concentration to mineral concentrations. The
conversion may be effected by multiplying each element
concentration by the ratio of molecular weight of a mineral to the
atomic weight of an element of interest. The method may further
comprise adding all mineral concentrations together to obtain the
amount of inorganic solids. The method may further comprise using a
calibration relationship between an actual amount of inorganic
solids, obtained by taking offline samples, filtering solids out,
and weighing dried filtered solids, and the measured amount of
inorganic solids, to calibrate the measured amount of inorganic
solids.
Other aspects and features of the present invention will become
apparent to those ordinarily skilled in the art upon review of the
following description of specific embodiments of the invention in
conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the present invention will now be described, by way
of example only, with reference to the attached figures,
wherein:
FIG. 1 is a flow diagram of a prior art paraffinic froth treatment
process;
FIG. 2 is a schematic of a system for controlling bitumen quality
according to a disclosed embodiment;
FIG. 3 is a flow diagram of a process for controlling bitumen
quality according to a disclosed embodiment;
FIG. 4 is a non-limiting graph illustrating correlations between
nickel content and asphaltene content in bitumen, and between
vanadium content and asphaltene content in bitumen;
FIG. 5 is a graph identifying quartz (SiO.sub.2) by a Scanning
Electron Microscope and Energy Dispersive X-Ray (SEM-EDS) in PFT
bitumen;
FIG. 6 is a graph identifying kaolinite
(Al.sub.2Si.sub.2O.sub.5(OH).sub.4) by SEM-EDS in PFT bitumen;
FIG. 7 is a graph identifying calcite (C.sub.aCO.sub.3) by an
SEM-EDS in PFT bitumen;
FIG. 8 is a graph identifying pyrite (FeS.sub.2) by an SEM-EDS in
PFT bitumen;
FIG. 9 is a graph identifying anatase (TiO.sub.2) by an SEM-EDS in
PFT bitumen;
FIG. 10 is a schematic illustrating non-destructive continuous
measurement of certain mineral elements in PFT bitumen in
accordance with a disclosed embodiment; and
FIG. 11 is a calibration graph relating X-Ray Fluorescence (XRF)
total solids concentration with actual total solids
concentration.
DETAILED DESCRIPTION
"Solvent-assisted bitumen extraction" as used herein is a process
used to extract bitumen from mined oil sands using solvent. The
solvent may be, but is not limited to, a paraffinic (saturated
aliphatic) solvent. The extraction process may be aqueous or
non-aqueous.
"Hydrocarbon stream" as used herein means a stream stemming from
mined oil sands, which comprises hydrocarbons, and which has been
processed using a bitumen extracting solvent. The hydrocarbon
stream may be, but is not limited to, a hydrocarbon leg following
bitumen extraction using a paraffinic bitumen extracting solvent or
a hydrocarbon leg following bitumen extraction using a non-aqueous
bitumen extracting solvent.
"Bitumen quality" as used herein is an indicator of the amount of
selected contaminants in the process stream. Of course, lower
amounts of contaminants mean a higher bitumen quality. Contaminants
may include, but are not limited to, asphaltenes (comprising metal
porphyrins) and inorganic or mineral solids (comprising inorganic
elements, e.g. Si, Al, Ti, Fe, Na, K, Mg, and Ca).
"Bitumen froth quality" as used herein means a composition of
bitumen, water and solids in the feed bitumen-froth to a solvent
extraction unit. A higher quality of bitumen-froth comprises higher
concentrations of bitumen and lower concentrations of solids.
"Asphaltenes" as used herein are pentane insoluble, toluene soluble
components of carbonaceous materials such as bitumen, crude oil, or
coal. Generally, asphaltenes comprise carbon, hydrogen, nitrogen,
oxygen, sulfur, vanadium and nickel. As mentioned earlier, a
portion of the asphaltenes in bitumen is precipitated during
bitumen-froth treatment using a paraffinic solvent.
A brief background of metal porphyrins will now be provided.
Viscous hydrocarbons, for example bitumen, comprise relatively
large quantities of metals, mainly vanadium and nickel, much of
which is believed to be complexed in chemical structures called
porphyrins. These metal porphyrins tend to be predominantly present
in the asphaltenes, whose precipitation in the PFT process tends to
lower their concentrations and those of Ni and V in the product
bitumen.
Described herein is a method of controlling bitumen quality in a
hydrocarbon stream within a solvent-assisted bitumen extraction
operation, for instance a hydrocarbon stream from a froth
separation unit (FSU). Bitumen quality refers to the amounts of
selected contaminants in the process stream. Contaminants may
include asphaltenes (comprising metal porphyrins) and inorganic
solids (comprising inorganic elements, e.g. Si, Al, Ti, Fe, Na, K,
Mg, and Ca). Contaminants may also include sulfur. First, the
amounts of selected contaminants are measured. Next, these measured
values are compared to maximum reference values. Where one or more
of these contaminants is higher than the maximum reference value,
at least one variable of the solvent-assisted bitumen extraction is
adjusted to improve bitumen quality.
The contaminants may be measured indirectly by measuring their
constituent elements and then using established correlations
relating the contaminants with the constituent elements. The
correlations between contaminants and the constituent elements may
be established from laboratory or plant data.
The asphaltenes contaminant may be indirectly measured using the
correlations between measured nickel and/or vanadium content in the
hydrocarbon stream and asphaltene content. FIG. 4 is a non-limiting
graph illustrating correlations between nickel content and
asphaltene content in bitumen, and between vanadium content and
asphaltene content in bitumen. From these correlations, maximum
nickel and/or vanadium reference values could be selected which are
representatives of a maximum asphaltene reference value so that
adjustments to the process could be made based on the measured
nickel and/or vanadium content, without necessarily measuring or
estimating the asphaltene content.
The inorganic solids contaminant may be indirectly measured from
the measured inorganic elements (Si, Al, Ti, Fe, Na, K, Mg, and
Ca). The steps involved for doing this, according to one embodiment
of this invention, are described below.
The sulfur contaminant may be directly measured.
One method to measure the asphaltenes and inorganic solids
contaminants is by measuring vanadium, nickel and inorganic
elements (Si, Al, Ti, Fe, Na, K, Mg, and Ca) by X-Ray Fluorescence
(XRF). Other methods include, but are not limited to, Inductively
Coupled Plasma (ICP), Atomic Absorption (AA), and Electron Spin
Resonance (ESR). The above methods may also be used to measure the
sulfur contaminant.
One way of practicing an embodiment of the present invention is
illustrated in FIG. 2 in which a paraffinic solvent (202) (for
example, pentane or hexane mixed with isomers of pentanes or
hexanes) is metered and pumped through a metering pump (204) to the
froth stream (206) metered through a metering pump (205). The froth
and the solvent are well mixed in an on-line static mixer (not
shown in FIG. 2) before it enters the FSU (208). For the sake of
simplicity, only one FSU vessel is shown in FIG. 2.
In the FSU (208), the water along with asphaltenes and fines settle
out at the bottom and are removed as the water leg (210) from the
vessel. The diluted PFT bitumen (212) exits from the top of the
vessel. An on-line X-Ray Fluorescence (XRF) unit (213) measures the
amounts of selected contaminants in a portion of the hydrocarbon
leg (216). A feedback control system compares these measured
amounts with the maximum reference values of these contaminants. If
the measured contaminant amount is higher than the maximum
reference value, the control system sends a signal (214) to one or
both of the metering pumps (204 and 205) to adjust the amount of
solvent or froth, or both. The portion (215) of the hydrocarbon leg
exiting the XRF unit (213) is also shown.
Various other adjustments to the solvent-assisted process could be
made. Non-limiting examples include solvent to bitumen froth ratio,
amount of solvent feed, amount of bitumen froth feed, residence
time in the separation vessel, temperature in the separation
vessel, pressure in the separation vessel, bitumen froth quality,
or the addition of additives to accelerate the particle
settling.
FIG. 3 is a flow chart of one embodiment. The method shown in FIG.
3 comprises the following steps:
measuring: (i) an amount of nickel or vanadium, or both, as an
indication of asphaltene content, and optionally estimating an
asphaltene content based on the amount of nickel or vanadium, or
both; and (ii) an amount of inorganic elements as an indication of
inorganic solids content, and optionally estimating an amount of
inorganic solids based on the amount of inorganic elements
(302);
comparing the measured or estimated amounts of (i) and (ii) to
maximum reference values (304); and
where the measured or estimated amounts of (i) or (ii) are higher
than the maximum reference value, adjusting at least one variable
of the solvent-assisted bitumen extraction to control the
asphaltene content or the inorganic solids content in the
hydrocarbon stream (306).
As described above, the measured amount of nickel or vanadium, or
both, may be converted to asphaltenes content. The reason that this
is optional is that, the method is purposed to control asphaltene
content, and if a relationship between the amount of nickel,
vanadium, or both and asphaltene content has already been
established, the method may omit the step of actually estimating
the asphaltene content and simply compare the measured amount of
nickel, vanadium, or both, to the maximum reference value for
nickel, vanadium, or both. If the measured value is converted to an
estimated asphaltene value, this estimated value can be compared to
the maximum asphaltene reference value. This equally applies to the
optional step of estimating the inorganic solids content step.
As mentioned above, methods according to embodiments of the instant
invention may be used with non-aqueous solvent extraction streams.
By way of example only, the following references are mentioned, all
of which relate to non-aqueous extraction: Sparks et al., Fuel 1992
(71); 1349-1353; Canadian Patent Application 2,068,895 of Sparks et
al.; and U.S. Pat. No. 4,057,486 of Meadus et al.
In one embodiment, the following three steps may be performed to
determine the solid content in the hydrocarbons stream.
Step 1: Identifying Minerals by X-Ray Diffraction (XRD) or
SEM-EDS
The minerals in the solids are first identified using XRD or
SEM-EDS. This is done offline occasionally to make sure the mineral
types in the product have been correctly identified. Typical
minerals identified in PFT bitumen are quartz (SiO.sub.2),
kaolinite (Al.sub.2Si.sub.2O.sub.5(OH).sub.4), calcite
(CaCO.sub.3), pyrite (FeS.sub.2) and titanium-bearing minerals such
as anatase (TiO.sub.2), as shown in the graphs of FIGS. 5 to 9,
obtained by an SEM-EDS. The cps on the y-axis in these figures
represents X-ray counts per second and keV on the x-axis stands for
kiloelectron volt.
Step 2: Measuring Key Elements in Identified Minerals and
Converting to Mineral Concentration.
As shown in FIG. 10, key elements (e.g., Si, Al, Fe, Ti, Ca) in the
identified minerals are then measured on-line continuously using
XRF (with an X-ray source (1002) and a detector (1004) on a slip
stream (1006) taken from the main stream (1008) of the PFT bitumen.
The analyzed slip stream (1006a) is re-combined with the main
stream (1008). The key element concentrations are then converted to
corresponding mineral concentrations by multiplying each elemental
concentration by the ratio of the molecular weight of the mineral
and the element of interest. Some elements (e.g., Si) originating
from more than one minerals are distributed among their source
minerals. All the mineral concentrations thus determined are added
up to provide the total XRF-measured mineral concentrations.
The non-destructive, continuous measurement of the key elements
allows real-time data collection without loss of any product
stream.
Step 3: Converting XRF Mineral Concentrations to Total Solids
Concentrations
To fine tune the solids quantification, a calibration graph
relating the actual solids concentrations with the XRF-measured
concentrations (from Step 2) is generated. The actual solids
concentrations are determined offline by taking samples, filtering
the solids out and weighing the dried filtered solids.
Any change in the mineral types in the bitumen product during
operation of the plant is monitored from time to time through
examination of the minerals using XRD or SEM-EDS. Any change is
reflected in Steps 2 and 3.
In addition to measuring the solids on-line, the process may be
controlled to achieve product with target solids level. This is
accomplished by measuring the solids concentration on-line on a
slip stream, and sending a signal to take corrective action through
a feedback control loop.
The solids measurements and feedback loop can also be implemented
in the product bitumen coming out of the SRU after the solvent has
been recovered. This embodiment will allow measurements of
elements, whose concentrations may be too low for detection and
measurement in the diluted bitumen from the FSU, but high enough
for detection and measurement in the SRU product bitumen.
EXAMPLES
Example 1
Using Inorganic Elements to Determine Solids Content
To determine the solids content from the measured inorganic
elements, the following steps were used.
Step 1: Identifying Minerals by SEM-EDS or XRD
Five minerals were identified by SEM-EDS in the solids from the
bitumen in a PFT pilot conducted by IOR at CANMET (Canada Centre
for Mineral and Energy Technology). The names of the minerals,
their formulas and molecular weights are shown in Table 1. The key
elements in these minerals are Si, Al, Ca, Fe and Ti.
TABLE-US-00001 TABLE 1 Properties of Minerals Identified by SEM-EDS
in PFT Bitumen Solids Minerals Formula MW Quartz SiO2 60.09
Kaolinite Al.sub.2Si.sub.2O.sub.5(OH).sub.4 258.13 Calcite
CaCO.sub.3 100.09 Pyrite FeS.sub.2 119.98 Anatase TiO.sub.2
79.87
Step 2: Measuring Key Elements by XRF and Converting to Mineral
Concentration
For the purpose of this illustration, it is assumed that an on-line
XRF instrument has been used to measure the concentrations of the
key elements, as shown in the second column of Table 2.
To determine the mineral concentrations of kaolinite
(Al.sub.2Si.sub.2O.sub.5(OH).sub.4, calcite (CaCO.sub.3), pyrite
(FeS.sub.2) and anatase (TiO.sub.2), the Al, Ca, Fe, and Ti
concentrations were each multiplied by the ratio of the
corresponding mineral MW to the key element's atomic weight (Column
4, Table 2).
To determine the mineral concentrations of quartz (SiO.sub.2), the
Si concentration of 5.20 ppm corresponding to the kaolinite was
subtracted from the total 45 ppm of Si measured and then the
remaining 39.80 ppm of Si (from quartz) was multiplied by the ratio
of the MW of quartz to Si. This led to a quartz concentration of
85.14 ppm in the product bitumen.
The total minerals concentration was then added up to provide total
solids of 178.14 ppm by XRF in the PFT product bitumen.
TABLE-US-00002 TABLE 2 Measured Elemental, Converted Minerals and
Total Solids Concentration by XRF Calc. Total Measured Minerals
Solids by Conc. Minerals Conc. XRF Elements ppm Type ppm ppm 178.14
Al 5 Al.sub.2Si.sub.2O.sub.5(OH).sub.4 23.92 Ca 10 CaCO.sub.3 24.97
Fe 5 FeS.sub.2 10.74 Ti 20 TiO.sub.2 33.37 Si (from Quartz and 45
Quartz 85.14 Kaolinite)* *Si from Kaolinite 5.20 *Si from Quartz
39.80
Step 3: Converting XRF Solids to Actual Solids Concentration
Through Calibration
A calibration graph relating the actual solids to the XRF solids
(Step 2) was generated by taking samples of the PFT product bitumen
and determining the solids through filtration, drying and weighing.
Some hypothetical data on solids by XRF and actual solids measured
offline in the lab are shown below to illustrate the calibration.
FIG. 11 shows a linear relationship for the hypothetical data.
This calibration graph can be used to convert XRF measured total
solids concentration (Step 2) to the "actual" solids
concentration.
TABLE-US-00003 TABLE 3 Solids Concentration by XRF and Actual
Solids Concentration for Calibration Solids Conc. by Actual Solids
Conc. XRF (ppm) (ppm) 178.14 195 200 225 250 270 150 174
Example 2
Using V or Ni to Determine Asphaltenes Content
To determine the asphaltenes content in the product bitumen, V and
Ni were measured using atomic absorption (these could alternatively
be determined using an on-line XRF). A calibration graph or
equation relating V to asphaltenes content in the bitumen was
prepared. The equation is: V (ppm)=59.9+8.05 (asphaltenes in
bitumen, wt %). The asphaltene content can be determined using the
above equation by measuring the V in the product bitumen and
compared with the target asphaltene concentration range. By
incorporating the equation in the computer program of the control
algorithm, at least one process variable may be adjusted to achieve
the target asphaltene level in the bitumen product.
A calibration graph or equation relating Ni to asphaltenes content
in the bitumen was also prepared. The equation is: Ni
(ppm)=18.1+3.18 (asphaltenes in bitumen, wt %). The asphaltene
content can be determined using the above equation by measuring the
Ni in the product bitumen and compared with the target asphaltene
concentration range. By incorporating the equation in the computer
program of the control algorithm, at least one process variable may
be adjusted to achieve the target asphaltene level in the product
bitumen.
In the preceding description, for purposes of explanation, numerous
details are set forth in order to provide a thorough understanding
of the embodiments of the invention. However, it will be apparent
to one skilled in the art that these specific details are not
required in order to practice the invention.
Embodiments of the disclosure can be represented as a computer
program product stored in a machine-readable medium (also referred
to as a computer-readable medium, a processor-readable medium, or a
computer usable medium having a computer-readable program code
embodied therein). The machine-readable medium can be any suitable
tangible, non-transitory medium, including magnetic, optical, or
electrical storage medium including a diskette, compact disk read
only memory (CD-ROM), memory device (volatile or non-volatile), or
similar storage mechanism. The machine-readable medium can contain
various sets of instructions, code sequences, configuration
information, or other data, which, when executed, cause a processor
to perform steps in a method according to an embodiment of the
disclosure. Those of ordinary skill in the art will appreciate that
other instructions and operations necessary to implement the
described implementations can also be stored on the
machine-readable medium. The instructions stored on the
machine-readable medium can be executed by a processor or other
suitable processing device, and can interface with circuitry to
perform the described tasks.
The above-described embodiments of the invention are intended to be
examples only. Alterations, modifications and variations can be
effected to the particular embodiments by those of skill in the art
without departing from the scope of the invention, which is defined
solely by the claims appended hereto.
* * * * *